1. Field of the Invention
The present invention relates to an improved process for alkoxylating active hydrogen compounds by reaction with an alkylene oxide of from 2 to 4 carbon atoms.
2. Description of the Related Art
Narrow distribution or "peaked" alkoxylates having a narrow molecular weight or homolog distribution are becoming increasingly important, since they have better application properties than the ordinary, broad distribution alkoxylates which are normally prepared using alkali metal hydroxides or alkoxides as catalysts. They find use in the main as surfactants in detergent and cosmetic compositions, but also in the paper and the textile fiber industries. There is therefore an urgent need for efficient processes for synthesizing such narrow distribution alkoxylates.
U.S. Pat. No. 3,957,922 (1) relates to a process for preparing alkoxylated products using aluminum or iron compounds as catalysts. The iron compounds mentioned are iron salts of customary mineral acids such as iron(III) chloride, iron(III) sulfate, iron(II) chloride, iron(II) sulfate, iron(II) nitrate and iron(III) phosphate, iron salts of fatty acids, iron powders, hydrates of iron(III) chloride and iron(II) chloride and sulfate and also commercial iron-coated catalyst materials.
EP-B-090,445 (2) relates to a process for polymerizing epoxides using double metal cyanide complexes as catalysts. These complexes may contain iron(III) and iron(II) atoms. It is also possible for water-soluble iron(III) salts to be present.
U.S. Pat. No. 4,727,199 (3) describes heterogeneous alkoxylation catalysts consisting of a metal oxide bonded to an anion. One of the metal oxides mentioned is iron oxide. The anion-bound metal oxide catalysts are amorphous or predominantly amorphous.